Hydraulic fluid containing alkyl 1,2,3,4,7,7 - hexachlorobicyclo-(2.2.1)-hept-2-ene-5-carboxylate base

ABSTRACT

FLAMEPROOF HYDRAULIC FLUID AND METHOD OF TRANSMITTING POWER EMPLOYING FLUID HAVING AS A BASE AN ALKYL 1,2,3,4,7,7HEXACHLOROBICYCLO-(2.2.1)-HEPT-2-ENE-5-CARBOXYLATE.

HYDRAULIC FLUID CONTAINING ALKYL 1,2,3,4,7,7 HEXACHLOROBICYCLO-[2.2.1]- HEPT-Z-ENE-S-CARBOXYLATE BASE Bruce W. Hotten, Orinda, Califi, assignor to Chevron Research Company, San Francisco, Calif. No Drawing. Filed May 21, 1968, Ser. No. 730,955 Int. Cl. (309k 3/00 US. Cl. 252-75 17 Claims ABSTRACT OF THE DISCLOSURE Flameproof hydraulic fluid and method of transmitting power employing fluid having as abase an alkyl 1,2,3,4,7,7- hexachlorobicyclo-[2.2.1] -hept-2-ene-S-carboxylate.

BACKGROUND OF THE INVENTION The growth of automated industrial equipment has greatly increased the need for nonflammable hydraulic oils. A number of materials have been employed in the past for this purpose. Included among these are the socalled phosphate fluids, or phosphate esters of various types. These materials, while extensively employed in aircraft because of their low densities, are not especially suitable for heavy industrial use precisely because of the low density; high density fluids act as much better power transfer agents. Also, the phosphate materials are low in flame resistance and have low viscosity indices, requiring the addition of substantial amounts of various viscosity index improvers in order to make them suitable for use over a variety of temperature ranges. This addition usually results in even lower flame resistance. Other materials that are often employed are chlorinated alkanes, such as chlorinated waxes. However, these materials require chlorination in the order of at least 40% to achieve substantial flame resistance, and at such a chlorine concentration, have viscosities so high that they are unsuitable for low temperature operation and also have low viscosity indices. Chlorinated arenes, also commonly used, have extremely low viscosity indices.

The importance of high viscosity index in a hydraulic fluid results from the fact that systems are often required to :be operated at considerable variations in temperature. Thus, if a fluid that is employed has a very low viscosity index, it will be suitable for operation over only a very limited temperature range. Thus, if it is desired to change the operating range of the equipment, 1t is necessary to drain the fluid from the system and replace it with one of suitable viscosity range for the desired temperature of operation. The viscosity index is especially important since hydraulic fluids usually serve a lubricating function as well as simply being a means of power transmission. Therefore, a fluid which becomes low in viscosity at high temperatures, or extremely viscous at low temperatures, will fail to lubricate properly.

SUMMARY It has now been found that an improved method of transmitting hydraulic power comprises applying force to a flame resistant power transmission medium having, as a base, a chlorinated unsaturated ester which is an alkyl 1,2,3,4,7,7-hexachlorobicyclo[2.2.1] hept 2 cue-5- carboxylate. The fluid bases are of the following formula:

United States Patent 3,574,117. Patented Apr. 6, 1971 in which R is an alkyl group of from 4 to 18 carbon atoms, X is hydrogen or methyl, and Y is hydrogen or lower alkyl. R is preferably alkyl of from 6 to 16 carbon atoms. X and Y are preferably hydrogen.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The esters which are employed in the compositions and methods of this invention are prepared in a typical Diels- Alder type reaction from an ester of an a-B unsaturated carboxylic acid and hexachlorocyclopentadiene. Reference to the general type of reaction involving hexachlorocyclopentadiene may be found in an article by C. W. Roberts, Chemistry of Hexachlorocyclopentadiene," Chemistry and Industry, Feb. 1, 1958, pp. -115. In an alternate procedure, an unsaturated aliphatic acid may be adducted to the diene and the resulting acid may then be esterified with a suitable alcohol. Transesterification with other esters may be employed, also.

In general, the Diels-Alder .adduction is carried out at temperatures of from about 70 to 200 C. In the case of the present preparations, a preferred temperature range is from about to 180 C. The reaction is simply carried out by mixing and heating the diene (hexachlorocyclopentadiene) with the dienophile (ester of lZ-fi unsaturated acid) and stirring for a period of 2 to 8 hours.

Examples of suitable acids used to produce the ester reactants are acrylic, methacrylic, crotonic, isocrotonic, apentenoic, etc. Acrylic acid is preferred. The acids are esterified with various straightand branched-chain alcohols of from 4 to 18 carbon atoms. Examples of the alcohols include butyl, amyl, hexyl, octyl, decyl, dodecyl, hexadecyl, octadecyl, etc. The preferred alcohols contain from 6 to 16 carbon atoms. Straight-chain materials are preferred.

The following examples illustrate the preparation of the fluids employed in this invention:

EXAMPLE 1 Preparations of butyl 1,2,3 ,4,7,7-hexachlorobicyclo [2.2. 1]

hept-2-ene-5-carboxylate 819.00 g. (3 moles) of hexachlorocyclopentadiene (molecular weight 273) were placed in a resin flask fitted with a condenser, thermometer, nitrogen inlet, and dropping funnel. 384.51 g. (3 moles) of butyl acrylate (mo lecular weight 128.17) were added through the dropping funnel while the mixture was being stirred. No reaction was observed. A heating mantle was applied to the flask and the heat was gradually increased. At a temperature of about C., the temperature began to rise rapidly, indicating an exothermic reaction. The temperature rose to 235 C. rapidly. The mixture was allowed to cool, and infrared analysis was obtained. The mixture was reheated to C. and held for 1 hour. LR. showed no change in the product after the initial exothermic reaction. The heating was continued for an additional hour at 150 C. LR. analysis again indicated no change. The material was then cooled, yielding a yellow, slightly cloudy fluid. The material was filtered and the following tests were obtained:

Viscosity, 100 F.3 0.25 centistokes Viscosity, 210 F.4.3 centistokes Pour point45 F. V. I.-7 .63 Neutron activation analysis:

Percent chlorine (52.4 theoretical)-55 .3 Percent oxygen (8.0 theoretical)8.07 Refractive index1 .5214, 1.5191 Density-4.466, 1.458

The product obtained above was Washed with Water three times to remove any possible remaining acid, then dried by warming on a steam plate with nitrogen bubbling. The material was essentially neutral. The following analysis was obtained by neutron activation:

Percent chlorine (52.4 theoretical) 5 3 .5 Percent oxygen (8.0 theoretical)--8.2

EXAMPLE 2 Preparation of butyl 1,2,3,4,7,7-hexachloro-5-methylbicyclo-[2.2.1]-hept-2-ene-S-carboxylate The general procedure of Example 1 was followed, employing 355.0 g. (2.5 moles) of butyl methacrylate and 682.5 g. (2.5 moles) of hexachlorocyclopentadiene. The reaction temperature was maintained at 150 C. for a period of about 11 hours. The material was topped to a distillation temperature of -130 C. (pot temperature 150 C.). The residue, which showed no trace of unreacted methacrylate by I.R., weighed 657 g. and exhibited the following characteristics:

Viscosity, 100 F.-1386 centistokes Viscosity, 210 F.-75.04 centistokes V.'I.-112 Pour point-+l F. Refractive index1.5 1 18 Density1.345 Neutron activation analysis:

Percent chlorine (50.6 theoretical)-41.5 Percent oxygen (7.7% theoretica1)11.7

EXAMPLE 3 Preparation of 1,2,3,4,7,7-hexachlorobicyclo- [2.2.1]-hept-2-ene-5-carboxylic acid 216 g. (3 moles) of glacial acrylic acid, 819 g. of hexachlorocyclopentadiene, and 1,035 g. of glacial acetic acid were placed in a resin flask fitted with condenser, drying tube, and nitrogen inlet. The material was heated for a period of about 5 hours at 120130- C. The mixture was then cooled and charged with water precipitating a white solid. The water was removed by filtration, followed by 3 water washes. The material was dried overnight under vacuum and then washed with mixed hexanes to remove unreacted diene. 730' g. of product was recovered. The material melted in the range of 154l81 C. and had an acid number of 150 (theoretical 164). The sample analyzed 63% chlorine (theoretical 62%) and 9.9% oxygen (theoretical 9.3%).

EXAMPLE 4 Preparation of octyl 1,2,3,4,7,7-hexachlorobicyclo- [2.2.1]-hept-2-ene-5-carboxylate 69 g. (0.2 mole) of the acid produced in Example 3 and 26 g. (0.2 mole) of normal octyl alcohol were placed in a 3-necked flask fitted with condenser takeoff, thermometer, stirrer, and nitrogen inlet. The mixture was heated over a period of 2 hours to 140 C. Some reflux began at 110 C. 1.4 ml. of water was removed. The following day, the temperature was raised to 150 C. and held for about 6 hours. The total takeoff of water was 2.5 ml. The product was placed in a beaker and heated on the steam plate under nitrogen to remove free Water. Analysis of the sample by neutron activation showed 43.2% chlorine (theoretical 46%); 8.2% oxygen (theoretical 7%). The material had an acid number of 8.3, pH 5.3.

EXAMPLE 5 Preparation of dodecyl l,2,3,4,7,7-hexachlorobicycle-[2.2.1]-hept-2-ene-S-carboxylate The procedure of Example 4 was followed, employing 69 g. (0.2 mole) of the acid product of Example 3 and 37.2 g. (0.2 mole) of dodecyl alcohol. The analysis of the product by neutron activation showed 42.8% chlorine (theoretical 41%); 7.2% oxygen (theoretical 6.2%).

EXAMPLE 6 Preparation of 2-ethylhexyl l,2,3,4,7,7-hexachlorobicyclo-[2.2.1]-hept-2-ene-5-carboxylate Following the general procedure of Example 1, 736 g. (4 moles) of 2-ethylhexyl acrylate was reacted with 1,092 g. (4 moles) of hexachlorocyclopentadiene. The reaction yielded 1,777 g. of a yellow liquid product which showed, by neutron activation analysis, a chlorine content of 46.9 (theoretical 46) and an oxygen content of 7.2 (theoretical 7).

EXAMPLE 7 Preparation of 1,4,5,6,7,7-hexachlorobicyclo- [2.2. 1 -hept-5-ene-2-yl butyrate In order to form the reverse ester of the preceding examples, 171.0 g. (1.5 moles) of vinyl butyrate was reacted With 409.5 g. of hexachlorocyclopentadiene. The chlorocyclodiene was placed in a resin flask equipped with stirrer, thermometer, condenser, and dropping funnel. The ester was added dropwise at 25 C. from a dropping funnel. The mixture was heated at a temperature of to 147 C. over a 1 /2 hour period. After cooling, infrared analysis indicated no reaction had taken place. The mixture was raised to a temperature of 155 C. and, after 1 /2 hours of heating, some reaction had taken place. Heating was continued for another 5 hours at a temperature of 130 to 150 C. Analysis indicated formation of the Diels-Alder adduct. The product was black, fluid, and of net weight 574 g. The material was topped at 150 C. (pot temperature) under a pressure of 3 mm. Hg. A total of 42 ml. of yellow distillate was removed (-I.R. indicating primarily hexachlorocyclopentadiene). The yield after topping was 496 g. 90 g. of the product was distilled under 0.3 mm. Hg to a distillation temperature of 126 C. The distillation yielded 10 ml. of a clear yellow liquid showing the following properties:

(neutron activation)55 .5 (theoretical EXAMPLE 8 Preparation of 1,4,5,6,7,7-hexachlorobicyclo- [2.2.1]hept-5-ene-2-yl hexanoate The procedure of Example 7 was followed, employing 47.0 g. of vinyl hexanoate and 90.4 g. of the hexachlorocyclopentadiene. The product was quite dark, as was the product of Example 7 indicating very poor thermal stability, and distillation under a vacuum of 0.2 to 0.3 mm. Hg produced only 10.5 ml. distillate.

A primary advantage in the use of the chlorinated bicycloheptene ester base fluids as power transmission media lies in the high viscosity indices of the materials compared with previously used flame resistant fluids. Thus, this feature, combined with excellent flame resistance and thermal stability, makes them suitable for use in a wide variety of hydraulic power transmission applications. The following table shows the viscosity and pour point characteristics of the chlorinated bicyclo heptene esters compared with representative commercially available, flame-proof hydraulic fluids. The commercial materials include a chlorinated wax-based material designated A and a chlorinated biphenyl-based material designated B.

TABLE I.PHYSICAL PROPERTIES OF CHLORINATED BICYCLOHEPTENE ESTERS Viscosity Viscosity Pour R from alcohol 100 F., 210 F., Viscosity point, Fluid portion of ester centistokes centistokes index F;

Example 1 n-Butyl 30.00 4. 3 7. 63 -45 Example 2 do 1, 386 75.0 112 Example 4 n-Octyl 43 5.6 61 -44 Example 5 n-DodecyL 50 6. 3 80 -43 Example 6 Z-ethylhexyl 65 6 1 Example 7 Reverse ester from 4. l 4. 7 30 --35 vinyl butyrate. Example 8 Reverse ester from 36 4. 7 2

vinyl hexanoate. A 3, 600 145 60 B 40 3 Negative From these data, itmay be seen that the chlorinated bicycloheptene esters, with the exception of Example 2 in which some polymerization occurred, have viscosities at 100 F. in a range making them suitable for use in relatively low temperature systems. Note that A, a commercially available chlorinated Wax material, has a viscosity at 100 F. of 3600, making it entirely unsuitable for use at that temperature. The subject esters also have positive and quite acceptable viscosity indices, indicating that they may be used without additional viscosity additive over a wide temperature range. The pour points of the esters are also in a range that will allow their functioning at low temperatures.

Upon prolonged heating at temperatures exceeding 400 F., the subject esters remain fluid, while the reverse esters of Examples 7 and 8 become tarry, and the ester of Example 8 loses its acid group upon vacuum topping at 150 C.

In order to demonstrate the flame resistance of the fluids, they were subjected to the following commonly employed flammability tests: Flash Point Test (ASTM D9257), Autogenous Ignition Test (ASTM D-286 5ST) and a Pipe Wick Test in which passes through the flame before ignition are recorded. Reference to the latter test may be found in Aeronautical Material Specifications 3150-C (Society of Automotive Engineers). Data from these tests comparing the esters with commercial fluid A are included in Table II following. Additionally, data from a Paint Compatibility Test, which involves placing a sample of the fluid on an enamel surface and allowing it to remain for days, is included.

TABLE IL-FLAME RESISTANCE OF CHLORO- BICYCLOHEPTENE ESTERS It may be seen that the esters have high flash points, are resistant to ignition in the Pipe Wick Test and display a high autogenous ignition temperature. The esters also are not harmful to enamel coatings. A commercial phosphate base high temperature fluid completely stripped the paint in the Paint Compatibility Test.

The material of Example 4 was also subjected to a Rubber Swell Test, in which a Buna-N O-ring was immersed in the fluid for 72 hours at a temperature of 160 F. The swelling was measured at 42% compared with 91% for a commercial phosphate base fluid.

In using the fluids in hydraulic systems, it is necessary to employ, in addition to the ester bases, certain conventional hydraulic fluid additives. 7

Thus, for prolonged use, the fluids must contain a conventional acid acceptor, a conventional antioxidant, or a combination of both. For use in systems in which iron or steel will be contacted by the fluid, the use of a conventional rust inhibitor is necessary. Other conventional additives such as viscosity index improvers, dyes, oiliness agents, etc., may also be used.

The oxidation inhibitors which may be used in the fluids are, as noted, conventional materials for functional fluid use in general. The preferred materials are the arylamines and the hindered phenols. However, also suitable are a large variety of materials which have conventionally been used in functional fluids as antioxidants and anticorrodents.

Thus, in addition to the amines and phenols, materials may be employed such as phenothiazines, hydroxy anthracenes, metal dithiocarbamates and dithiocarbamate esters, dialkyl monosulfides, disulfides, alkyl sulfonamides, diaryl monosulfides, tetra-alkyl titanates, etc.

A general description of the antioxidants may be found in Scott, Atmospheric Oxidation and Antioxidants, Elsevier, Amsterdam, 1965. Particular reference to the most suitable antioxidants may be found on pp. 251 et seq. under Lubricating Oil Antioxidants.

Examples of the diarylamine inhibitors which may be used include diphenylamine, phenyl-ot-naphthylamine, and phenyl-B-naphthylamine, and the alkylated derivatives of these compounds containing alkyl groups of from 1 to 20 carbons atoms; and related compounds such as 4,4-diaminodiphenyl methane, etc.

Suitable phenolic inhibitors include bis-phenol alkanes, bis-phenol sulfides, dihydroxy diphenyls, acylamino phenols, dihydroxybenzenes, and various p-tertiary alkyl bridged phenols, such as p-tert. butyl phenol, etc. A wide variety of these materials are disclosed in the Scott reference, previously mentioned, especially on pages 283-290.

The acid acceptors which are employed in the fluids are materials which act as proton acceptors and prevent the buildup of corrosive acids in the fluids when they undergo decomposition under prolonged use at high temperatures. A preferred class of materials is the epoxy compounds, especially epoxidized naturally occurring material, such as epoxidized unsaturated glycerides, etc. Examples of suitable materials include epoxidized soybean oil, epoxidized castor oil, epoxidized linseed oil, epoxidized fats, etc. Other suitable materials include epoxy esters such as butyl epoxy acetoxy stearate, glyceryl triepoxy acetoxy stearate, isooctyl epoxy stearate, epoxidized isooctyl tallate, etc. In general, the acid portion of the simple esters and the glycerides will have from about 10 to 30 carbon atoms.

Also suitable are various alkyl and aralkyl epoxides such as epoxy decane, epoxy dodecane, epoxy hexadecane, epoxy octadecane, epoxy eicosane, etc. Cyclo-aliphatic epoxides, such as cyclododecane, pinene oxide, etc., are also suitable. 10-30 carbons are preferred with these materials.

Also suitable are glycidol and various glycidol others, such as glycidol phenyl ether, glycidol allyl ether, 2,2- bis(p-phenyl glycidoxy) propane, etc.

Other suitable acid acceptors are the metal alkyl phenates, and their sulfurized derivatives. Especially preferred are the overbased materials in which a base reserve is provided by the ratio of equivalents of alkaline earth to equivalents of phenol substantially greater than that in the normal salts. As noted, both the sulfonated and unsulfonated materials have been over-based. Many methods of overbasing have been disclosed; typical materials are set forth in U.S. Pat. Nos. 3,178,368, 3,194,761, and 3,336,224. A typical normal sulfurized alkaline earth phenate may be represented by the formula in which R represents the alkyl radicals on the benzene ring, and M is an alkaline earth metal. The sulfur is attached to both rings. Other configurations are possible, i.e., rather than two like rings being connected in the above example, attachment may be made to an alkaryl, aryl, alkyl, or alkyl-aryl group.

The metals may be aluminum, cobalt, chromium, sodium, lead, etc., or an alkaline earth metal such as calcium, barium, strontium, or magnesium. The preferred metal is calcium.

Another important class of acid acceptors which may be used are the oil-soluble salts of high molecular weight sulfonic acid usually produced by the treatment of petroleum oils with fuming sulfuric acid.

The over-based materials which are equivalent to the over-based phenates are preferred.

The sulfonic acids generally have molecular weights from about 350 to 650. Many patents have described the material; typical are U.S. 2,454,736 and U.S. 2,467,176. Overbased materials are described in U.S. 2,833,716 and many other patents.

The acid acceptors and oxidation inhibitors are employed in minor amounts, sutficient to prevent decomposition of the fluid and attacks upon the hydraulic systems. Amounts of from 0.1 to by weight are usually suflicient; 0.1 to 5% is preferred.

The rust inhibitors which may be used include a wide variety of materials commonly employed in functional fluids. Thus, the rust inhibitors may include high molecular weight amines, alkyl maleamides, other amides, alkyl and alkenyl succinic acids, pyromellitic acid amide, trimellite acid amides, etc. Specific examples of useful inhibitors include acyl sarcosines, such as oleyl sarcosine, ethoxylated soybean amine, the maleamide produced from reaction of maleic anhydride and soybean amine, amide from the reaction of alkenyl succinic anhydride (C -C alkenyl) with dibutylamine and an amide produced by reaction of alkenyl succinic anhydride with diethylamine. The amide type of rust inhibitor is preferred.

The rusting inhibitors are generally present in amounts of from 0.1 to 5% by weight, a preferred range being from about 0.5 to 2%.

In addition to the additives previously mentioned, other conventional additives may be employed in the compositions. For example, supplementary oxidation inhibitors such as the various phenolic inhibitors and diarylamine inhibitors may be used. While the fluid bases themselves have outstanding viscosity indices, it may be desirable in many applications to include commonly used viscosity index improvers in order to achieve even higher viscosity indices. Examples of these inhibitors are the acryloids, etc. Dyes, sludge inhibitors, antifoaming agents, etc., may also be included.

The hydraulic systems in which the methods and compositions of this invention are very useful are, as previously noted, industrial systems used to transmit power to various items of machinery. These systems are becoming increasingly important in industry because of the ease with which they may be adapted to automatic and computerized control. In general, two major components characterize the systems. These components are a means to impart pressure to the fluid and a second means for converting the pressure to useful mechanical motion. These components usually are piston or vane-type pumps; however, other high pressure pumps are suitable. Secondary components of the systems usually include a reservoir for storage of fluid, means to control the flow, such as valves, and means, such as pipes, to conduct the fluid from the reservoir to the pump and to the motor.

The pumps which are used to impart pressure to the fluid and the hydraulic motors which receive energy from the fluid are constructed to minimize leakage at high pressures. Thus, close tolerances must be maintained in equipment, and the hydraulic fluids must lubricate the parts as well as transmit power. Thus, the fluids of this invention are especially advantageous for use in these systems because of their high viscosity indices and low pour points which allow lubrication of the parts subject to wear over quite wide temperature ranges, from about 40 F. to over 300 F.

What is claimed is:

1. A method of transmitting power which comprises applying force to a hydraulic power transmission fluid which consists essentially of an alkyl 1,2,3,4,7,7-hexachlorobicyclo-[2.2.l]-hept-2-ene-5-carb0xylate of the formula:

in which R is an alkyl group of from 4 to 18 carbon atoms, X is hydrogen or methyl, and Y is hydrogen or lower alkyl.

2. The method of claim 1, in which X and Y are hydrogen.

3. The method of claim 2, in which R contains from 6 to 16 carbon atoms.

4. The method of claim 3, in which R is substantially straight chain.

5. The method of claim 1, wherein the power transmission fluid contains from 0.1 to 10% by weight of an acid acceptor selected from the group consisting of epoxy compounds, overbased metal alkylphenates, overbased sulfurized metal alkylphenates, and oil-soluble salts of high molecular weight sulfonic acids.

6. The method of claim 1, wherein the power transmission fluid contains from 0.1 to 10% by Weight of an arylamine or hindered phenol antioxidant.

7. The method of claim 6, wherein the power transmission fluid contains, in addition, from about 0.1 to about 5% by weight of an amine or amide rust inhibitor.

8. A power transmission fluid consisting essentially of a major portion of an alkyl 1,2,3,4,7,7-hexachlorobicyclo- [2.2.1]-hept-2-ene-S-carboxylate of the formula:

in which R is an alkyl group of from 4 to 18 carbon atoms, X is hydrogen or methyl, and Y is hydrogen or lower alkyl, and a minor portion of an acid acceptor selected from the group consisting of epoxy compounds, overbased metal alkylphenates, overbased sulfurized metal alkylphenates, and oil-soluble salts of high molecular weight sulfonic acids.

9. The fluid of claim 8, in which X and Y are hydrogen.

10. The fluid of claim 9, in which R contains from 6-16 carbon atoms.

11. The fluid of claim 10, in which R is substantially straight chain.

12. The fluid of claim 8, in which the acid acceptor is an overbased metal alkyl phenate or an oil-soluble salt of a high molecular weight sulfonic acid.

13. The fluid of claim 8 which contains an additional References Cited minor portion of an arylamine or hindered phenol anti- UNITED STATES PATENTS oxidant.

I 3,371,108 2/1968 Dissen 252--54.6X dialrtlagliiefiuld of claim 13, 111 which the antioxidant 1s a 5 3,489,792 1/1970 Greenbaum et a1 0X 15. The flllld of claim 14, in WhlCh the dlarylamine 1s Ho ten 252 75 phenyl-a-naphthylamine. LEON D. \ROSDOL, Primary Examiner 16. The fluid of claim 8, which containsanadditional SILVERSTEIN Assistant Examiner minor portion of an arnlne or amlde rust inhibltor. 1O

17. The fluid of claim 16, in which the rust inhibitor Us ()1 is an alkyl maleamide. 25276, 77, 78 

